Typically, an engine having an exhaust gas recirculation device is provided a device for cooling the EGR gas by a coolant (hereinafter referred to as “EGR cooler”). In the case where soot or the like in the EGR gas deposits inside the EGR gas channel, the cooling capacity (heat exchange efficiency between the EGR gas and the coolant inside the EGR cooler) of the EGR cooler is decreased. In the case where the cooling capacity of the EGR cooler is decreased, the EGR gas is recirculated to the intake channel while being hot, the intake channel may be damaged by overheating. Therefore, it is desired to detect a reduction in the cooling capacity of the EGR cooler and notify the same to a user.
Japanese Patent Laying-Open No. 2008-261297 (PTL 1) discloses a technique which determines that in a structure configured to supply a coolant to an EGR cooler by using a mechanical water pump driven by the power of an engine, the cooler is abnormal if the temperature of the EGR gas is higher than the temperature of the coolant by a predefined value or more, and determines that the cooling capacity of the EGR cooler is decreased if the abnormality determination count is not less than a first predefined value when the engine is rotating at a low rotational speed and the abnormality determination count is not less than a second predefined value when the engine is rotating at a high rotational speed.